An independent scientist’s observations on society, technology, energy, science and the environment. “Modern science has been a voyage into the unknown, with a lesson in humility waiting at every stop. Many passengers would rather have stayed home.” – Carl Sagan

Home exposure to radon, a naturally occurring radioactive decay product of radium, has been thought to be the second leading cause of lung cancer, after cigarette smoking. Chemically inert, it can percolate out of the ground into basements.

The study was initiated and managed by Donald F. Nelson, now professor emeritus of physics at WPI, during the 1990s, a time when concern over the link between residential radon exposure and lung cancer was growing. Nelson says the aim was to try to establish what level of radon exposure actually correlated with significant lung cancer risk and to establish a safety zone for home radon levels.

The results of the study were described by their own authors as “surprising” and “stunning”: Clear evidence of radiation hormesis. It looks like Bernard Cohen has been vindicated after all.

“We were certainly not looking for a hormetic effect,” says co-author Joel H. Popkin of Fallon Clinic and St. Vincent Hospital in Worcester. “Indeed, we were stunned when the data pointed to that conclusion in such a strong way.”

A study of lung cancer risk from residential radon exposure and its radioactive progeny was performed with 200 cases (58% male, 42% female) and 397 controls matched on age and sex, all from the same health maintenance organization. Emphasis was placed on accurate and extensive year-long dosimetry with etch-track detectors in conjunction with careful questioning about historic patterns of in-home mobility. Conditional logistic regression was used to model the outcome of cancer on radon exposure, while controlling for years of residency, smoking, education, income, and years of job exposure to known or potential carcinogens. Smoking was accounted for by nine categories: never smokers, four categories of current smokers, and four categories of former smokers. Radon exposure was divided into six categories (model 1) with break points at 25, 50, 75, 150, and 250 Bq m-3, the lowest being the reference. Surprisingly, the adjusted odds ratios (AORs) were, in order, 1.00, 0.53, 0.31, 0.47, 0.22, and 2.50 with the third category significantly below 1.0 (p < 0.05), and the second, fourth, and fifth categories approaching statistical significance (p < 0.1). An alternate analysis (model 2) using natural cubic splines allowed calculating AORs as a continuous function of radon exposure. That analysis produces AORs that are substantially less than 1.0 with borderline statistical significance (0.048 <= p <= 0.05) between approximately 85 and 123 Bq m-3. College-educated subjects in comparison to high-school dropouts have a significant reduction in cancer risk after controlling for smoking, years of residency, and job exposures with AOR = 0.30 (95% CI: 0.13, 0.69), p = 0.005 (model 1).

It will be very interesting to keep an eye on research in this area in the future, especially given the famous debates between the likes of Bernard Cohen and William Field over their radon dose response research.

he evidence against the linear model and for radiation hormesis has been solid as a rock for 40 years. Yet the LNT model prevails. Why? Follow the money and the politics. Health-physics science is divided, roughly along the lines of who puts money before principles. There have been some amazingly bitter fights within the health physics community. A look at the historical background of radiation research is instructive.

After World War II, the details were released of the A-bombing of Japan. Studies of atomic bomb survivors from Hiroshima and Nagasaki, showed a linear relationship between cancer mortality and high doses of radiation as a result fallout hysteria became one of the themes of the times. The situation was not helped by lurid stories of several high dose incidents reported in the press. Health Physics and Genetics were supported lavishly by radiation fears, and Radiation Biology became the most intensely researched science in history. Health physicists soon learned that their livelihood depended upon scaring funds out of governments and science became irrelevant if the paymasters wanted to mislead the public about the hazards of radiation. If a particular study failed to find evidence of radiation’s ill effects, the data was simply forced into the LNT model. Yet some of these studies are among the best evidence for radiation hormesis because the authors were not looking for it, and effectively denied that it existed.

The justification for using the LNT model was that too many test animals or too much time would be needed to evaluate chronic dose rates. If the LNT model is correct, there is no “no observed adverse effect level” (NOAEL) for regulators to observe, thus officials responsible for public health can claim justification in calling for minimization of exposures to ionizing radiation. Note that this is tantamount to saying that avoiding sunlight is justified on the grounds that nobody will get sunburns in the dark. Added to this, during the Cold War a number of people promoted the LNT model in an attempt to discourage all uses of nuclear weapons and nuclear power, and used it as leverage in their campaigns.

No, it won’t go away easily, but who would have thought a Black would be running for President of the U.S or that gay folks would get married openly thirty years ago? Things do change.